Showrunner Shonda Rhimes told TVLine in January that she was resolved to designing a fitting finale to Grey’s current eighth season, despite not knowing which members of the original cast would and would not return next fall.

“[It] was the most complex puzzle I’ve had to put together — ever,” she shared. ”We have all these moveable pieces of who’s coming back and who’s not, and finally I just decided to focus on what was going to be best creatively [and] make it work regardless of what is happening [off screen].”

ABC has yet to formally order a ninth season of Grey’s; the network reveals its 2012-13 TV schedule next Tuesday.